Gravity induced flow cell
The flow cell includes first and second reservoirs having a selected volume containing a flowable redox electrode. A membrane separates charged and discharged material. An energy-extraction region includes electronically conductive porous current collectors through or adjacent to which the flowable redox electrodes flow and to which charge transfer occurs. Structure is provided for altering orientation of the flow cell whereby gravity induces flow of the flowable redox electrode between the first and second reservoirs to deliver power. By varying the angle of the cell, flow rate and power delivered on discharge or the charge rate on charge may be varied.
1. Gravity induced flow cell comprising:
first and second reservoirs having a selected volume containing a flowable redox electrode;
a membrane separating charged and discharged material;
an energy-extraction region including electronically conductive porous current collectors through or adjacent to which the flowable redox electrode flows and to which charge transfer occurs; and
structure for altering orientation of the flow cell continuously with respect to gravity in the range of about 0 to about 35 degrees whereby gravity passively induces flow of the flowable redox electrode along a flow direction between the first and second reservoirs without pumps and valves, wherein the structure is configured to change flow rate and power delivered on discharge or charge rate on charge by varying the angle of the cell with respect to gravity,
wherein the first reservoir is disposed on a first end of the energy extraction region, the second reservoir is disposed on a second end, opposite the first end, of the energy extraction region, the first end and the second end defining an axis along the flow direction.
2. The flow cell of claim 1 further including a motor to vary angle of the cell.
3. The flow cell of claim 1 wherein the energy-extraction region has a volume and the ratio of the volume of the energy-extraction region to reservoir volume is selected to be in the range of about 1 to about 100.
4. The flow cell of claim 1 further including structure for providing pneumatic pressure to alter flow rate.
5. The flow cell of claim 1 further including valves to modulate flow rates.
6. The flow cell of claim 1 wherein the electronically conductive porous current collectors comprise carbon.
7. The flow cell of claim 6 wherein the carbon is selected from the group consisting of glassy carbon, disordered carbon, and graphite.
8. The flow cell of claim 6 wherein the carbon is in the form of compacted fibers, woven fibers, paper or 3D reticulated foam.
9. The flow cell of claim 1 wherein the electronically conductive porous current collectors are a metal or metal alloy.
10. The flow cell of claim 9 wherein the metal is selected from the group consisting of aluminum, copper, nickel and stainless steel.
11. The flow cell of claim 1 wherein the electronically conductive porous current collectors are coated with a metal or metal alloy.
12. The flow cell of claim 1 wherein the energy-extraction region comprises current collector plates.
13. The flow cell of claim 1 wherein the flowable redox electrode is a suspension.
14. The flow cell of claim 13 wherein the suspension includes conductor particles.
15. The flow cell of claim 1 wherein the reservoirs and energy-extraction region include a slippery, low friction or non-wetting surface.
16. The flow cell of claim 1 wherein the flowable redox electrode is a Li-polysulfide suspension.
17. The flow cell of claim 1 having a flowable redox electrode working ion that is an alkali ion selected from the group consisting of lithium, sodium, potassium and cesium.
18. The flow cell of claim 1 having a flowable redox electrode working ion that is a divalent ion of magnesium or calcium.
19. The flow cell of claim 1 having a flowable redox electrode working ion that is a trivalent ion of aluminum or yttrium.